The invention is directed to the field of neutron detection and measurement of neutron energies. The invention has special application to technologies where a relatively low neutron flux rate is observed.
Neutron detectors which measure the presence of neutrons, namely neutron flux, as opposed to energy, are known in the art. Examples of such detectors are counters or ionization chambers filled with boron containing gases such as BF.sub.3 in which neutrons are detected by the production of ionizing alpha particles when the neutron reacts with boron-10. For fast neutrons, ionization chambers may also be fabricated by utilizing a hydrogenous gas and taking advantage of the elastic scattering of protons which are subsequently utilized to ionize the gas.
When neutron energy measurements are desired, as opposed to flux measurements, the art teaches utilization of time-of-flight methods in which the travel times of individual neutrons are measured, where again the neutrons are detected at the end point by means of an ionization counter.
Since the announcement of "cold fusion" from experiments of Steven E. Jones et al. at Brigham Young University, there has been a demand for neutron counters which can measure neutron energies at very low rates. Such counters are necessary in confirming or refuting the existence of catalyzed fusion in which deuterons are infused into a host material with a resulting enhancement of nuclear fusion. In such systems, detection of the neutrons at the expected energy provides verification of the reaction process and a measure of the reaction rate. One such detector, called a coincidence calorimeter, is described in the inventors prior U.S. Pat. No. 4,931,649 entitled "Neutron Coincidence Calorimeter," incorporated herein by reference.
An interesting observation which has materialized from cold fusion research has been the discovery of neutron "bursts". It is of great interest to measure the number of neutrons in a particular burst as well as their temporal distribution. It is also of interest to measure the energy of neutrons from a low flux source such as from cold fusion sources.